diff --git a/src/google/protobuf/stubs/port.h b/src/google/protobuf/stubs/port.h
index 3c7ada385c..0fcee68918 100644
--- a/src/google/protobuf/stubs/port.h
+++ b/src/google/protobuf/stubs/port.h
@@ -51,7 +51,7 @@
   #if !defined(PROTOBUF_DISABLE_LITTLE_ENDIAN_OPT_FOR_TEST)
     #define PROTOBUF_LITTLE_ENDIAN 1
   #endif
-  #if _MSC_VER >= 1300 && !defined(__INTEL_COMPILER)
+  #if defined(_MSC_VER) && _MSC_VER >= 1300 && !defined(__INTEL_COMPILER)
     // If MSVC has "/RTCc" set, it will complain about truncating casts at
     // runtime.  This file contains some intentional truncating casts.
     #pragma runtime_checks("c", off)